INTERNATIONAL MARITIME ORGANIZATION

IMO

E

A 18/Res.749 23 November 1993 Original: ENGLISH ASSEMBLY - 18th session Agenda item 11 RESOLUTION A.749(18) adopted on 4 November 1993 CODE ON INTACT STABILITY FOR ALL TYPES OF SHIPS COVERED BY IMO INSTRUMENTS THE ASSEMBLY, RECALLING Article 15(j) of the Convention on the International Maritime Organization concerning the functions of the Assembly in relation to regulations and guidelines concerning maritime safety, RECOGNIZING the need for the development of an internationally agreed code on intact stability for all types of ships covered by IMO instruments, which would summarize the work carried out by the Organization so far, HAVING CONSIDERED the recommendations made by the Maritime Safety Committee at its sixty-second session, 1. ADOPTS the Code on Intact Stability for All Types of Ships Covered by IMO Instruments, set out in the Annex to the present resolution, which supersedes the following recommendations: (a) Recommendation on intact stability for passenger and cargo ships

under 100 metres in length (resolution A.167(ES.IV)); (b) Amendments to the recommendation on intact stability for passenger

and cargo ships under 100 metres in length (resolution A.167(ES.IV)) with respect to ships carrying deck cargoes (resolution A.206(VII));

(c) Recommendation on intact stability of fishing vessels

(resolution A.168(ES.IV)); and (d) Recommendation on a severe wind and rolling criterion (weather

criterion) for the intact stability of passenger and cargo ships of 24 metres in length and over (resolution A.562(14));

2. INVITES Governments concerned to use the provisions of the Code as a basis for relevant safety standards, unless their national stability requirements provide at least an equivalent degree of safety; 3. RECOMMENDS Governments concerned to ensure that inclining tests are conducted in accordance with the guidelines specified in the Annex to the present resolution; 4. AUTHORIZES the Maritime Safety Committee to amend the Code as necessary in the light of further studies and experience gained from the implementation of the provisions contained therein.

ANNEX CODE ON INTACT STABILITY FOR ALL TYPES OF SHIPS COVERED BY IMO INSTRUMENTS CONTENTS Preamble Chapter 1 - General 1.1 Purpose 1.2 Application 1.3 Definitions Chapter 2 - General provisions against capsizing and information for the master 2.1 Stability booklet 2.2 Operating booklets for certain ships 2.3 General precautions against capsizing 2.4 Fixed ballast 2.5 Operational procedures related to weather conditions Chapter 3 - Design criteria applicable to all ships 3.1 General intact stability criteria for all ships 3.2 Severe wind and rolling criterion (weather criterion) 3.3 Effect of free surface of liquids in tanks 3.4 Assessment of compliance with stability criteria 3.5 Standard loading conditions to be examined 3.6 Calculation of stability curves Chapter 4 - Special criteria for certain types of ships 4.1 Cargo ships carrying timber deck cargoes 4.2 Fishing vessels 4.3 Special purpose ships 4.4 Cargo ships carrying grain in bulk 4.5 Offshore supply vessels 4.6 Mobile offshore drilling units (MODUs) 4.7 Pontoons 4.8 Dynamically supported craft (DSC) 4.9 Containerships greater than 100 m Chapter 5 - Icing considerations 5.1 General 5.2 Cargo ships carrying timber deck cargo 5.3 Fishing vessels 5.4 Offshore supply vessels 24 m to 100 m in length 5.5 Dynamically supported craft

Chapter 6 - Considerations for watertight integrity 6.1 Hatchways 6.2 Machinery space openings 6.3 Doors 6.4 Cargo ports and other similar openings 6.5 Sidescuttles, window scuppers, inlets and discharges 6.6 Other deck openings 6.7 Ventilators, air pipes and sounding devices 6.8 Freeing ports 6.9 Miscellaneous Chapter 7 - Determination of lightship displacement and centres of gravity 7.1 Application 7.2 Definitions 7.3 Preparation for the inclining test 7.4 Plans required 7.5 Test procedure 7.6 Determination of ships' stability by means of rolling period tests

(for ships up to 70 m in length) 7.7 Inclining test for MODUs 7.8 Stability test for pontoons Annex 1 - Detailed guidance for the conduct of an inclining test Annex 2 - Recommendations for skippers of fishing vessels on

ensuring a vessel's endurance in conditions of ice formation

PREAMBLE 1 This Code has been assembled to provide, in a single document, recommended provisions relating to intact stability, based primarily on existing IMO instruments. Where recommendations in this Code appear to differ with other IMO Codes, such as the MODU Code or DSC Code, the other Codes should be taken as the prevailing instrument. For the sake of completeness and for the convenience of the user, this Code also contains relevant provisions from mandatory IMO instruments. Such requirements have been identified with an asterisk. However, in all cases, the authoritative text for requirements is contained in the mandatory instruments. 2 Criteria included in the Code are based on the best "state of art" concepts taking into account sound design and engineering principles and experience gained from operating such ships. Furthermore, design technology for modern ships is rapidly evolving and the Code should not remain static but be re-evaluated and revised, as necessary. To this end, the Organization will periodically review the Code taking into consideration both experience and further development. 3 Throughout the development of the Code it was recognized that in view of a wide variety of types, sizes of ships and their operating and environmental conditions, problems of safety against accidents related to stability have generally not yet been solved. In particular, the safety of a ship in a seaway involves complex hydrodynamic phenomena which up to now have not been adequately investigated and understood. Ships in a seaway should be treated as a dynamical system and relationships between ship and environment conditions like wave and wind excitations are recognized as extremely important elements. It is recognized that development of stability criteria, based on hydrodynamic aspects and stability analysis of a ship in a seaway, poses, at present, complex problems which require further research.

CODE ON INTACT STABILITY FOR ALL TYPES OF SHIPS COVERED BY IMO INSTRUMENTS CHAPTER 1 - GENERAL 1.1 Purpose The purpose of the Code on Intact Stability for All Types of Ships Covered by IMO Instruments, hereinafter referred to as the Code, is to recommend stability criteria and other measures for ensuring the safe operation of all ships to minimize the risk to such ships, to the personnel on board and to the environment. 1.2 Application 1.2.1 This Code contains intact stability criteria for the following types of ships and other marine vehicles of 24 m in length and above unless otherwise stated: - cargo ships - cargo ships carrying timber deck cargo - cargo ships carrying grain in bulk - passenger ships - fishing vessels - special purpose ships - offshore supply vessels - mobile offshore drilling units - pontoons - dynamically supported craft - containerships 1.2.2 The coastal State may impose additional requirements regarding the design aspects of ships of novel design or ships not otherwise covered by the Code. 1.3 Definitions For the purpose of this Code the definitions given hereunder apply. For terms used, but not defined in this Code, the definitions as given in the 1974 SOLAS Convention apply. 1.3.1 Administration means the Government of the State whose flag the ship is entitled to fly. 1.3.2 A passenger ship is a ship which carries more than twelve passengers as defined in regulation I/2 of the 1974 SOLAS Convention, as amended. 1.3.3 A cargo ship is any ship which is not a passenger ship. 1.3.4 A fishing vessel is a vessel used for catching fish, whales, seals, walrus or other living resources of the sea.

1.3.5 A special purpose ship means a mechanically self-propelled ship which, by reason of its function, carries on board more than 12 special personnel as defined in paragraph 1.3.3 of the IMO Code of Safety for Special Purpose Ships (resolution A.534(13)), including passengers (ships engaged in research, expeditions and survey; ships for training of marine personnel; whale and fish factory ships not engaged in catching; ships processing other living resources of the sea, not engaged in catching or other ships with design features and modes of operation similar to ships mentioned above which, in the opinion of the Administration may be referred to this group). 1.3.6 An offshore supply vessel means a vessel which is engaged primarily in the transport of stores, materials and equipment to offshore installations and designed with accommodation and bridge erections in the forward part of the vessel and an exposed cargo deck in the after part for the handling of cargo at sea. 1.3.7 A mobile offshore drilling unit (MODU) or unit is a ship capable of engaging in drilling operations for the exploration or exploitation of resources beneath the sea-bed such as liquid or gaseous hydrocarbons, sulphur or salt: .1 a column-stabilized unit is a unit with the main deck connected to

the underwater hull or footings by columns or caissons; .2 a surface unit is a unit with a ship or barge-type displacement hull

of single or multiple hull construction intended for operation in the floating condition;

.3 a self-elevating unit is a unit with moveable legs capable of raising

its hull above the surface of the sea. 1.3.8 A dynamically supported craft (DSC) is a craft which is operable on or above water and which has characteristics so different from those of conventional displacement ships, to which the existing international conventions, particularly SOLAS and Load Line, apply, that alternative measures should be used in order to achieve an equivalent level of safety. Within the aforementioned generality, a craft which complies with either of the following characteristics would be considered a DSC: .1 if the weight, or a significant part thereof, is balanced in one mode

of operation by other than hydrostatic forces; .2 if the craft is able to operate at speeds such that the Froude number

is equal to or greater than 0.9. 1.3.9 An air-cushion vehicle is a craft such that the whole or a significant part of its weight can be supported, whether at rest or in motion, by a continuously generated cushion of air dependent for its effectiveness on the proximity of the surface over which the craft operates. Note: When the revision of the Intact Stability Code is undertaken, the

standards for dynamically supported craft will be replaced by the provisions of the High Speed Craft (HSC) Code currently under development.

1.3.10 A hydrofoil boat is a craft which is supported above the water surface in normal operating conditions by hydrodynamic forces generated on foils. 1.3.11 A side wall craft is an air-cushion vehicle whose walls extending along the sides are permanently immersed hard structures. 1.3.12 A containership means a ship which is used primarily for the transport of marine containers. 1.3.13 Freeboard is the distance between the assigned loadline and freeboard deck*. * For the purposes of application of chapters I and II of Annex I of the

1966 LL Convention to open-top containerships, "freeboard deck" is the freeboard deck according to the 1966 LL Convention as if hatch covers are fitted on top of the hatch cargo coamings.

CHAPTER 2 - GENERAL PROVISIONS AGAINST CAPSIZING AND INFORMATION FOR THE MASTER 2.1 Stability booklet 2.1.1 Stability data and associated plans should be drawn up in the official language or languages of the issuing country and the language of the master. If the languages used are neither English nor French the text should include a translation into one of these languages. 2.1.2* Each ship should be provided with a stability booklet, approved by the Administration, which contains sufficient information to enable the master to operate the ship in compliance with the applicable requirements contained in the Code. On a mobile offshore drilling unit, the stability booklet is referred to as an operating manual.* 2.1.3 The format of the stability booklet and the information included will vary dependent on the ship type and operation. In developing the stability booklet, consideration should be given to including the following information: .1 a general description of the ship; .2 instructions on the use of the booklet; .3 general arrangement plans showing watertight compartments, closures,

vents, downflooding angles, permanent ballast, allowable deck loadings and freeboard diagrams;

.4 hydrostatic curves or tables and cross curves of stability calculated

on a free-trimming basis, for the ranges of displacement and trim anticipated in normal operating conditions;

.5 capacity plan or tables showing capacities and centres of gravity for

each cargo stowage space; .6 tank sounding tables showing capacities, centres of gravity, and free

surface data for each tank; .7 information on loading restrictions, such as maximum KG or minimum GM

curve or table that can be used to determine compliance with the applicable stability criteria;

.8 standard operating conditions and examples for developing other

acceptable loading conditions using the information contained in the stability booklet;

.9 a brief description of the stability calculations done including

assumptions; .10 general precautions for preventing unintentional flooding; * Refer to regulation II-1/22 of the 1974 SOLAS Convention, as amended,

regulation 10 of the 1966 LL Convention and the 1988 LL Protocol and regulation III/10 of the 1993 Torremolinos Protocol.

.11 information concerning the use of any special cross-flooding fittings with descriptions of damage conditions which may require cross-flooding;

.12 any other necessary guidance for the safe operation of the ship under

normal and emergency conditions; .13 a table of contents and index for each booklet; .14 inclining test report for the ship, or: .1 where the stability data is based on a sister ship, the

inclining test report of that sister ship along with the lightship measurement report for the ship in question; or

.2 where lightship particulars are determined by other methods than

from inclining of the ship or its sister, a summary of the method used to determine those particulars;

.15 recommendation for determination of ship's stability by means of an

in-service inclining test. 2.1.4 As an alternative to the stability booklet mentioned in 2.1.2, a simplified booklet in an approved form containing sufficient information to enable the master to operate the ship in compliance with the applicable provisions of the Code may be provided at the discretion of the authority concerned. 2.1.5 As a supplement to the approved stability booklet, a loading computer may be used to facilitate the stability calculations mentioned in paragraph 2.1.3.9. 2.1.6 It is desirable that the input/output form in the computer and screen presentation be similar to the one in the stability booklet so that the operators will easily gain familiarity with the use of the stability booklet. 2.1.7 A simple and straightforward instruction manual written as per sound marine practice and in a language common to all officers should be provided with the loading computer. 2.1.8 In order to validate the proper functioning of the computer program, four loading conditions taken from the stability booklet (final) should be run in the computer periodically and the print-outs should be maintained on board as check conditions for future reference. 2.2 Operating booklets for certain ships Special purpose ships, dynamically supported craft and novel craft, should be provided with additional information in the stability booklet such as design limitations, maximum speed, worst intended weather conditions or other information regarding the handling of the craft that the master needs to operate the ship safely. 2.3 General precautions against capsizing 2.3.1 Compliance with the stability criteria does not ensure immunity against capsizing, regardless of the circumstances, or absolve the master

from his responsibilities. Masters should therefore exercise prudence and good seamanship having regard to the season of the year, weather forecasts and the navigational zone and should take the appropriate action as to speed and course warranted by the prevailing circumstances. 2.3.2 Care should be taken that the cargo allocated to the ship is capable of being stowed so that compliance with the criteria can be achieved. If necessary, the amount should be limited to the extent that ballast weight may be required. 2.3.3 Before a voyage commences, care should be taken to ensure that the cargo and sizeable pieces of equipment have been properly stowed or lashed so as to minimize the possibility of both longitudinal and lateral shifting, while at sea, under the effect of acceleration caused by rolling and pitching. 2.3.4 A ship, when engaged in towing operations, should not carry deck cargo, except that a limited amount, properly secured, which would neither endanger the safe working of the crew on deck nor impede the proper functioning of the towing equipment, may be accepted. 2.3.5 The number of partially filled or slack tanks should be kept to a minimum because of their adverse effect on stability. 2.3.6 The stability criteria contained in chapter 3 set minimum values, but no maximum values are recommended. It is advisable to avoid excessive values of metacentric height, since these might lead to acceleration forces which could be prejudicial to the ship, its complement, its equipment and to safe carriage of the cargo. 2.3.7 Regard should be paid to the possible adverse effects on stability where certain bulk cargoes are carried. In this connection, attention should be paid to the IMO Code of Safe Practice for Solid Bulk Cargoes. 2.4 Fixed ballast If used, fixed ballast should be installed under the supervision of the Administration and in a manner that prevents shifting of position. Fixed ballast should not be removed from the ship or relocated within the ship without the approval of the Administration. 2.5 Operational procedures related to weather conditions 2.5.1 All doorways and other openings through which water can enter into the hull or deckhouses, forecastle, etc., should be suitably closed in adverse weather conditions and accordingly all appliances for this purpose should be maintained on board and in good condition. 2.5.2 Weathertight and watertight hatches, doors, etc., should be kept closed during navigation, except when necessarily opened for the working of the ship and should always be ready for immediate closure and be clearly marked to indicate that these fittings are to be kept closed except for access. Hatch covers and flush deck scuttles in fishing vessels should be kept properly secured when not in use during fishing operations. All portable deadlights should be maintained in good condition and securely closed in bad weather. 2.5.3 Any closing devices provided for vent pipes to fuel tanks should be secured in bad weather.

2.5.4 Fish should never be carried in bulk without first being sure that the portable divisions in the holds are properly installed. 2.5.5 Reliance on automatic steering may be dangerous as this prevents ready changes to course which may be needed in bad weather. 2.5.6 In all conditions of loading necessary care should be taken to maintain a seaworthy freeboard. 2.5.7 In severe weather, the speed of the ship should be reduced if excessive rolling, propeller emergency, shipping of water on deck or heavy slamming occurs. Six heavy slammings or 25 propeller emergences during 100 pitching motions should be considered dangerous. 2.5.8 Special attention should be paid when a ship is sailing in following or quartering seas because dangerous phenomena such as parametric resonance, broaching to, reduction of stability on the wave crest, and excessive rolling may occur singularly, in sequence or simultaneously in a multiple combination, creating a threat of capsize. Particularly dangerous is the situation when the wave length is of the order of 1.0 - 1.5 ship's length. A ship's speed and/or course should be altered appropriately to avoid the above-mentioned phenomena. 2.5.9 Water trapping in deck wells should be avoided. If freeing ports are not sufficient for the drainage of the well, the speed of the ship should be reduced or course changed, or both. Freeing ports provided with closing appliances should always be capable of functioning and are not to be locked. 2.5.10 Masters should be aware that steep or breaking waves may occur in certain areas, or in certain wind and current combinations (river estuaries, shallow water areas, funnel shaped bays, etc.). These waves are particularly dangerous, especially for small ships. 2.5.11 Use of operational guidelines for avoiding dangerous situations in severe weather conditions or an on-board computer based system is recommended. The method should be simple to use. 2.5.12 Dynamically supported craft should not be intentionally operated outside the worst intended conditions and limitations specified in the Dynamically Supported Craft Permit to Operate, in the Dynamically Supported Craft Construction and Equipment Certificate, or in documents referred to therein.

CHAPTER 3 - DESIGN CRITERIA APPLICABLE TO ALL SHIPS 3.1 General intact stability criteria for all ships 3.1.1 Scope The following criteria are recommended for passenger and cargo ships. 3.1.2 Recommended general criteria 3.1.2.1 The area under the righting lever curve (GZ curve) should not be less than 0.055 metre-radians up to ? = 30 angle of heel and not less than 0.09 metre-radians up to ? = 40 or the angle of flooding ?f* if this angle is less than 40. Additionally, the area under the righting lever curve (GZ curve) between the angles of heel of 30 and 40 or between 30and ?f, if this angle is less than 40, should not be less than 0.03 metre-radians. 3.1.2.2 The righting lever GZ should be at least 0.20 m at an angle of heel equal to or greater than 30. 3.1.2.3 The maximum righting arm should occur at an angle of heel preferably exceeding 30 but not less than 25. 3.1.2.4 The initial metacentric height GMo should not be less than 0.15 m. 3.1.2.5 In addition for passenger ships, the angle of heel on account of crowding of passengers to one side as defined in paragraphs 3.5.2.6 to 3.5.2.9 should not exceed 10. 3.1.2.6 In addition for passenger ships, the angle of heel on account of turning should not exceed 10 when calculated using the following formula: V 2 M = 0.02 o ? (KG - d/2) R L MR = heeling moment in metre-tonnes Vo = service speed in m/s L = length of ship at waterline in m ? = displacement in tonnes d = mean draught in m KG = height of centre of gravity above keel in m 3.1.2.7 Where anti-rolling devices are installed in a ship, the Administration should be satisfied that the above criteria can be maintained when the devices are in operation. 3.1.2.8 A number of influences such as beam wind on ships with large windage area, icing of topsides, water trapped on deck, rolling * ?f is an angle of heel at which openings in the hull, superstructures or

deckhouses which cannot be closed weathertight immerse. In applying this criterion, small openings through which progressive flooding cannot take place need not be considered as open.

characteristics, following seas, etc., adversely affect stability and the Administration is advised to take these into account, so far as is deemed necessary. 3.1.2.9 Provisions should be made for a safe margin of stability at all stages of the voyage, regard being given to additions of weight, such as those due to absorption of water and icing (details regarding ice accretion are given in chapter 5) and to losses of weight such as those due to consumption of fuel and stores. 3.1.2.10 For ships carrying oil-based pollutants in bulk, the Administration should be satisfied that the criteria given in 3.1.2 can be maintained during all loading and ballasting operations. 3.1.2.11 See also general recommendations of an operational nature given in section 2.5 above. 3.2 Severe wind and rolling criterion (weather criterion) 3.2.1 Scope This criterion supplements the stability criteria given in section 3.1. The more stringent criteria of section 3.1 given above and the weather criterion should govern the minimum requirements for passenger or cargo ships of 24 m in length and over. 3.2.2 Recommended weather criterion 3.2.2.1 The ability of a ship to withstand the combined effects of beam wind and rolling should be demonstrated for each standard condition of loading, with reference to the figure as follows: .1 the ship is subjected to a steady wind pressure acting perpendicular

to the ship's centreline which results in a steady wind heeling lever (lw1).

.2 from the resultant angle of equilibrium (?o), the ship is assumed to

roll owing to wave action to an angle of roll (?1) to windward. Attention should be paid to the effect of steady wind so that excessive resultant angles of heel are avoided*;

.3 the ship is then subjected to a gust wind pressure which results in

a gust wind heeling lever (lw2); .4 under these circumstances, area "b" should be equal to or greater

than area "a"; .5 free surface effects (section 3.3) should be accounted for in the

standard conditions of loading as set out in section 3.5; * The angle of heel under action of steady wind (?o) should be limited to a

certain angle to the satisfaction of the Administration. As a guide, 16 or 80% of the angle of deck edge immersion, whichever is less, is suggested.

Figure - Severe wind and rolling The angles in the above figure are defined as follows: ?o = angle of heel under action of steady wind (see 3.2.2.1.2 and footnote) ?1 = angle of roll to windward due to wave action ?2 = angle of downflooding (?f) or 50 or ?c, whichever is less, where: ?f = angle of heel at which openings in the

hull, superstructures or deckhouses which cannot be closed weathertight immerse. In applying this criterion, small openings through which progressive flooding cannot take place need not be considered as open.

?c = angle of second intercept between wind

heeling lever lw2 and GZ curves. 3.2.2.2 The wind heeling levers lw1 and lw2 referred to in 3.2.2.1.1 and 3.2.2.1.3 are constant values at all angles of inclination and should be calculated as follows:

P.A.Z lw1 = (m) and 1000g? lw2 = 1.5 lw1 (m) where: P = 504 N/m2. The value of P used for ships in restricted service

may be reduced subject to the approval of the Administration; A = projected lateral area of the portion of the ship and deck

cargo above the waterline (m2); Z = vertical distance from the centre of A to the centre of the

underwater lateral area or approximately to a point at one half the draught (m);

? = displacement (t) g = 9.81 m/s2 3.2.2.3 The angle of roll (?1)* referred to in 3.2.2.1.2 should be calculated as follows: ?1 = 109k.X1.X2]5E[r.s (degrees) where: X1 = factor as shown in table 1 X2 = factor as shown in table 2 k = factor as follows: k = 1.0 for round-bilged ship having no bilge or bar keels k = 0.7 for a ship having sharp bilges k = as shown in table 3 for a ship having bilge keels, a bar keel or both r = 0.73 + 0.6 OG/d with : OG = distance between the centre of gravity and the waterline (m) (+ if centre of gravity is above the waterline, - if it is below) d = mean moulded draught of the ship (m) s = factor as shown in table 4. * The angle of roll for ships with anti-rolling devices should be determined

without taking into account the operation of these devices.

3.3 Effect of free surfaces of liquids in tanks For all conditions, the initial metacentric height and the stability curves should be corrected for the effect of free surfaces of liquids in tanks in accordance with the following assumptions: 3.3.1 Tanks which are taken into consideration when determining the effect of liquids on the stability at all angles of inclination should include single tanks or combinations of tanks for each kind of liquid (including those for water ballast) which according to the service conditions can simultaneously have free surfaces. 3.3.2 For the purpose of determining this free surface correction, the tanks assumed slack should be those which develop the greatest free surface moment, Mf.s. at a 30 inclination when in the 50 per cent full condition. 3.3.3 The values of Mf.s. for each tank may be derived from the formula: Mf.s. = vb k]5E[d where: Mf.s. is the free surface moment at any inclination in metre-tonnes v is the tank total capacity in cubic metres b is the tank maximum breadth in metres is the specific weight of liquid in the tank in cubic metre-tonnes d is equal to v (the tank block coefficient) blh h is the tank maximum height in metres l is the tank maximum length in metres k is the dimensionless coefficient to be determined from the following table according to the ratio b/h. The intermediate values are determined by interpolation. 3.3.4 Small tanks, which satisfy the following condition using the value of k corresponding to the angle of inclination of 30, need not be included in computation: vb k]DE[d 0.01m ? min where: ?min = minimum ship displacement in tonnes (metric tonnes). 3.3.5 The usual remainder of liquids in the empty tanks is not taken into account in computation.

Table of values for coefficient "k" for calculating free surface corrections 3.4 Assessment of compliance with stability criteria .1 For the purpose of assessing in general whether the stability

criteria are met, stability curves should be drawn for the main loading conditions intended by the owner in respect of the ship's operations.

.2 If the owner of the ship does not supply sufficiently detailed

information regarding such loading conditions, calculations should be made for the standard loading conditions.

3.5 Standard conditions of loading to be examined 3.5.1 Loading conditions The standard loading conditions referred to in the text of the present Code are as follows.

3.5.1.1 For a passenger ship: .1 ship in the fully loaded departure condition with full stores and

fuel and with the full number of passengers with their luggage; .2 ship in the fully loaded arrival condition, with the full number of

passengers and their luggage but with only 10% stores and fuel remaining;

.3 ship without cargo, but with full stores and fuel and the full number

of passengers and their luggage; .4 ship in the same condition as at .3 above with only 10% stores and

fuel remaining. 3.5.1.2 For a cargo ship: .1 ship in the fully loaded departure condition, with cargo

homogeneously distributed throughout all cargo spaces and with full stores and fuel;

.2 ship in the fully loaded arrival condition with cargo homogeneously

distributed throughout all cargo spaces and with 10% stores and fuel remaining;

.3 ship in ballast in the departure condition, without cargo but with

full stores and fuel; .4 ship in ballast in the arrival condition, without cargo and with

10% stores and fuel remaining. 3.5.1.3 For a cargo ship intended to carry deck cargoes: .1 ship in the fully loaded departure condition with cargo homogeneously

distributed in the holds and with cargo specified in extension and weight on deck, with full stores and fuel;

.2 ship in the fully loaded arrival condition with cargo homogeneously

distributed in holds and with a cargo specified in extension and weight on deck, with 10% stores and fuel.

3.5.2 Assumptions for calculating loading conditions 3.5.2.1 For the fully loaded conditions mentioned in 3.5.1.2.1, 3.5.1.2.2, 3.5.1.3.1 and 3.5.1.3.2 if a dry cargo ship has tanks for liquid cargo, the effective deadweight in the loading conditions therein described should be distributed according to two assumptions, i.e. with cargo tanks full, and with cargo tanks empty. 3.5.2.2 In the conditions mentioned in 3.5.1.1.1, 3.5.1.2.1 and 3.5.1.3.1 it should be assumed that the ship is loaded to its subdivision load line or summer load line or if intended to carry a timber deck cargo, to the summer timber load line with water ballast tanks empty. 3.5.2.3 If in any loading condition water ballast is necessary, additional diagrams should be calculated taking into account the water ballast. Its quantity and disposition should be stated.

3.5.2.4 In all cases, the cargo in holds is assumed to be fully homogeneous unless this condition is inconsistent with the practical service of the ship. 3.5.2.5 In all cases, when deck cargo is carried, a realistic stowage weight should be assumed and stated, including the height of the cargo. 3.5.2.6 A weight of 75 kg should be assumed for each passenger except that this value may be reduced to not less than 60 kg where this can be justified. In addition, the weight and distribution of the luggage should be determined by the Administration. 3.5.2.7 The height of the centre of gravity for passengers should be assumed equal to: .1 1.0 m above deck level for passengers standing upright.

Account may be taken, if necessary, of camber and sheer of deck; .2 0.30 m above the seat in respect of seated passengers. 3.5.2.8 Passengers and luggage should be considered to be in the spaces normally at their disposal, when assessing compliance with the criteria given in 3.1.2.1 to 3.1.2.4. 3.5.2.9 Passengers without luggage should be considered as distributed to produce the most unfavourable combination of passenger heeling moment and/or initial metacentric height, which may be obtained in practice, when assessing compliance with the criteria given in 3.1.2.5 and 3.1.2.6, respectively. In this connection, it is anticipated that a value higher than four persons per square metre will not be necessary. 3.6 Calculation of stability curves 3.6.1 General 3.6.1.1 Hydrostatic and stability curves should normally be prepared on a designed trim basis. However, where the operating trim or the form and arrangement of the ship are such that change in trim has an appreciable effect on righting arms, such change in trim should be taken into account. 3.6.1.2 The calculations should take into account the volume to the upper surface of the deck sheathing. In the case of wood ships, the dimensions should be taken to the outside of the hull planking. 3.6.2 Superstructures, deckhouses, etc., which may be taken into account 3.6.2.1 Enclosed superstructures complying with regulation 3(10)(b) of the 1966 Load Line Convention may be taken into account. 3.6.2.2 The second tier of similarly enclosed superstructures may also be taken into account. 3.6.2.3 Deckhouses on the freeboard deck may be taken into account, provided that they comply with the conditions for enclosed superstructures laid down in regulation 3(10)(b) of the 1966 Load Line Convention. 3.6.2.4 Where deckhouses comply with the above conditions, except that no additional exit is provided to a deck above, such deckhouses should not be

taken into account; however, any deck openings inside such deckhouses should be considered as closed even where no means of closure are provided. 3.6.2.5 Deckhouses, the doors of which do not comply with the requirements of regulation 12 of the 1966 Load Line Convention should not be taken into account; however, any deck openings inside the deckhouse are regarded as closed where their means of closure comply with the requirements of regulations 15, 17 or 18 of the 1966 Load Line Convention. 3.6.2.6 Deckhouses on decks above the freeboard deck should not be taken into account, but openings within them may be regarded as closed. 3.6.2.7 Superstructures and deckhouses not regarded as enclosed can, however, be taken into account in stability calculations up to the angle at which their openings are flooded (at this angle, the static stability curve should show one or more steps, and in subsequent computations the flooded space should be considered non-existent). 3.6.2.8 In cases where the ship would sink due to flooding through any openings, the stability curve should be cut short at the corresponding angle of flooding and the ship should be considered to have entirely lost its stability. 3.6.2.9 Small openings such as those for passing wires or chains, tackle and anchors, and also holes of scuppers, discharge and sanitary pipes should not be considered as open if they submerge at an angle of inclination more than 30. If they submerge at an angle of 30 or less, these openings should be assumed open if the Administration considers this to be a source of significant flooding. 3.6.2.10 Trunks may be taken into account. Hatchways may also be taken into account having regard to the effectiveness of their closures.

CHAPTER 4 - SPECIAL CRITERIA FOR CERTAIN TYPES OF SHIPS 4.1 Cargo ships carrying timber deck cargoes 4.1.1 Scope The provisions given hereunder apply to all ships of 24 m in length and over engaged in the carriage of timber deck cargoes. Ships that are provided with and make use of their timber load line should also comply with the requirements of the regulations 41 to 45 of the Load Line Convention. 4.1.2 Definitions The following definitions apply for the purposes of the present section: .1 timber means sawn wood or lumber, cants, logs, poles, pulpwood and

all other types of timber in loose or packaged forms. The term does not include wood pulp or similar cargo;

.2 timber deck cargo means a cargo of timber carried on an uncovered

part of a freeboard or superstructure deck. The term does not include wood pulp or similar cargo;*

.3 timber load line means a special load line assigned to ships

complying with certain conditions related to their construction set out in the International Convention on Load Lines and used when the cargo complies with the stowage and securing conditions of the Code of Safe Practice for Ships Carrying Timber Deck Cargoes, 1991 (resolution A.715(17)).

4.1.3 Recommended stability criteria For ships loaded with timber deck cargoes and provided that the cargo extends longitudinally between superstructures (where there is no limiting superstructure at the after end, the timber deck cargo should extend at least to the after end of the aftermost hatchway)** transversely for the full beam of ship after due allowance for a rounded gunwale not exceeding 4% of the breadth of the ship and/or securing the supporting uprights and which remains securely fixed at large angles of heel, the Administration may apply the following criteria which substitute those given in 3.1.2.1 to 3.1.2.4: .1 The area under the righting lever curve (GZ curve) should not be less

than 0.08 metre-radians up to ? = 40 or the angle of flooding if this angle is less than 40.

.2 The maximum value of the righting lever (GZ) should be at

least 0.25 m. * Refer to regulation 42(1) of the 1966 LL Convention. ** Refer to regulation 44(2) of the 1966 LL Convention.

.3 At all times during a voyage, the metacentric height GMo should be positive after correction for the free surface effects of liquid in tanks and, where appropriate, the absorption of water by the deck cargo and/or ice accretion on the exposed surfaces. (Details regarding ice accretion are given in chapter 5). Additionally, in the departure condition the metacentric height should be not less than 0.10 m.

4.1.4 Stability booklet 4.1.4.1* The ship should be supplied with comprehensive stability information which takes into account timber deck cargo. Such information should enable the master, rapidly and simply, to obtain accurate guidance as to the stability of the ship under varying conditions of service. Comprehensive rolling period tables or diagrams have proved to be very useful aids in verifying the actual stability conditions.* 4.1.4.2 For ships carrying timber deck cargoes, the Administration may deem it necessary that the master be given information setting out the changes in deck cargo from that shown in the loading conditions, when the permeability of the deck cargo is significantly different from 25% (see 4.1.6 below). 4.1.4.3 For ships carrying timber deck cargoes, conditions should be shown indicating the maximum permissible amount of deck cargo having regard to the lightest stowage rate likely to be met in service. 4.1.5 Operational measures 4.1.5.1 The stability of the ship at all times, including during the process of loading and unloading timber deck cargo, should be positive and to a standard acceptable to the Administration. It should be calculated having regard to: .1 the increased weight of the timber deck cargo due to: .1.1 absorption of water in dried or seasoned timber, and .1.2 ice accretion, if applicable (chapter 5); .2 variations in consumables; .3 the free surface effect of liquid in tanks; and .4 weight of water trapped in broken spaces within the timber deck

cargo and especially logs. 4.1.5.2 The master should: .1 cease all loading operations if a list develops for which

there is no satisfactory explanation and it would be imprudent to continue loading;

* Refer to regulation II-1/22 of the 1974 SOLAS Convention, as amended and

regulation 10(2) of the 1966 LL Convention and the 1988 LL Protocol.

.2 before proceeding to sea, ensure that: .2.1 the ship is upright; .2.2 the ship has an adequate metacentric height; and .2.3 the ship meets the required stability criteria. 4.1.5.3 The masters of ships having a length less than 100 m should also: .1 exercise good judgement to ensure that a ship which carries stowed

logs on deck should have sufficient additional buoyancy so as to avoid overloading and loss of stability at sea;

.2 be aware that the calculated GMo in the departure condition may

decrease continuously owing to water absorption by the deck cargo of logs, consumption of fuel, water and stores and ensure that the ship has adequate GMo throughout the voyage;

.3 be aware that ballasting after departure may cause the ship's

operating draught to exceed the timber load line. Ballasting and deballasting should be carried out in accordance with the guidance provided in the Code of Safe Practice for Ships Carrying Timber Deck Cargoes, 1991 (resolution A.715(17)).

4.1.5.4 Ships carrying timber deck cargoes should operate, as far as possible, with a safe margin of stability and with a metacentric height which is consistent with safety requirements but such metacentric height should not be allowed to fall below the recommended minimum, as specified in 4.1.3. 4.1.5.5 However, excessive initial stability should be avoided as it will result in rapid and violent motion in heavy seas which will impose large sliding and racking forces on the cargo causing high stresses on the lashings. Operational experience indicates that metacentric height should preferably not exceed 3% of the breadth in order to prevent excessive accelerations in rolling provided that the relevant stability criteria given in 4.1.3 are satisfied. This recommendation may not apply to all ships and the master should take into consideration the stability information obtained from the ship's stability booklet. 4.1.6 Calculation of stability curves In addition to the provisions given in 3.6, the Administration may allow account to be taken of the buoyancy of the deck cargo assuming that such cargo has a permeability of 25% of the volume occupied by the cargo. Additional curves of stability may be required if the Administration considers it necessary to investigate the influence of different permeabilities and/or assumed effective height of the deck cargo. 4.1.7 Loading conditions to be considered The loading conditions which should be considered for ships carrying timber deck cargoes are specified in 3.5.1.3. For the purpose of these loading conditions, the ship is assumed to be loaded to the summer timber load line with water ballast tanks empty.

4.1.8 Assumptions for calculating loading conditions The following assumptions are to be made for calculating the loading conditions referred to in 4.1.7: the amount of cargo and ballast should correspond to the worst service condition in which all the relevant stability criteria of 3.1.2.1 to 3.1.2.4 or the optional criteria given in 4.1.3, are met. In the arrival condition, it should be assumed that the weight of the deck cargo has increased by 10% due to water absorption. 4.1.9* Stowage of timber deck cargoes The stowage of timber deck cargoes should comply with the provisions of chapter 3 of the Code of Safe Practice for Ships Carrying Timber Deck Cargoes, 1991 (resolution A.715(17)).* 4.2 Fishing vessels 4.2.1 Scope The provisions given hereunder apply to decked seagoing fishing vessels as defined in 1.3.4. The stability criteria given in 4.2.3 and 4.2.4 below should be complied with for all conditions of loading as specified in 4.2.5, unless the Administration is satisfied that operating experience justifies departures therefrom. 4.2.2 General precautions against capsizing Apart from general precautions referred to in sections 2.3 and 2.5, the following measures should be considered as preliminary guidance on matters influencing safety as related to stability. .1 all fishing gear and other large weights should be properly stowed and

placed as low as possible; .2 particular care should be taken when pull from fishing gear might have

a bad effect on stability, e.g., when nets are hauled by power-block or the trawl catches obstructions on the sea-bed;

.3 gear for releasing deck load in fishing vessels carrying catch on

deck, e.g., herring, should be kept in good working condition for use when necessary;

.4 when the main deck is prepared for the carriage of deck load by

division with pound boards, there should be slots between them of suitable size to allow easy flow of water to freeing ports to prevent trapping of water;

.5 fish should never be carried in bulk without first being sure that the

portable divisions in the holds are properly installed; .6 reliance on automatic steering may be dangerous as this prevents

changes to course which may be needed in bad weather; .7 in all conditions of loading necessary care should be taken to

maintain a seaworthy freeboard. * Refer to regulation 44 of the 1966 LL Convention and the 1988 LL Protocol.

.8 particular care should be taken when the pull from fishing gear results in dangerous heel angles. This may occur when fishing gear fastens onto an underwater obstacle or when handling fishing gear, particularly on purse seiners, or when one of the trawl wires tears off. The heel angles caused by the fishing gear in these situations may be eliminated by employing devices which can relieve or remove excessive forces applied through the fishing gear. Such devices should not impose a danger to the vessel through operating in circumstances other than those for which they were intended.

4.2.3* Recommended general criteria* 4.2.3.1 The general intact stability criteria given in section 3.1.2 (paragraphs 3.1.2.1 to 3.1.2.3) should apply to fishing vessels having a length of 24 m and over, with the exception of requirements on the initial metacentric height GMo (paragraph 3.1.2.4) which, for fishing vessels, should not be less than 0.35 m for single deck vessels. In vessels with complete superstructure or vessels of 70 m in length and over the metacentric height may be reduced to the satisfaction of the Administration but in no case should be less than 0.15 m. 4.2.3.2 The adoption by individual countries of simplified criteria which apply such basic stability values to their own types and classes of vessels is recognized as a practical and valuable method of economically judging the stability. 4.2.3.3 Where arrangements other than bilge keels are provided to limit the angle of roll, the Administration should be satisfied that the stability criteria referred to in 4.2.3.1 are maintained in all operating conditions. 4.2.4 Severe wind and rolling criterion (weather criterion) for fishing vessels 4.2.4.1 Fishing vessels of 45 m in length and over having large windage area should comply with the provisions of section 3.2 of the Code. 4.2.4.2 For fishing vessels in the length range between 24 m and 45 m the values of wind pressure (see 3.2.2.2) is to be taken from the following table:

h(m) 1

2

3

4

5

6 and over

P(N/m2) 316

386

429

460

485

504

where h is the vertical distance from the centre of the projected vertical area of the ship above waterline, to the waterline. 4.2.5* Loading conditions to be considered** 4.2.5.1 The standard loading conditions referred to in 4.2.1 are as follows: * Refer to regulation III/2 of the 1993 Torremolinos Protocol. ** Refer to regulation III/7 of the 1993 Torremolinos Protocol.

.1 departure conditions for the fishing grounds with full fuel, stores, ice, fishing gear, etc;

.2 departure from the fishing grounds with full catch; .3 arrival at home port with 10% stores, fuel, etc., remaining and full

catch; .4 arrival at home port with 10% stores, fuel, etc., and a minimum catch,

which should normally be 20% of full catch but may be up 40% provided the Administration is satisfied that operating patterns justify such a value.

4.2.5.2 Assumptions for calculating loading conditions should be as follows: .1 allowance should be made for the weight of the wet fishing nets and

tackle, etc., on deck; .2 allowance for icing, where this is anticipated to occur should be made

in accordance with the provisions of section 5.3; .3 in all cases the cargo should be assumed to be homogenous unless this

is inconsistent with practice; .4 in conditions referred to in 4.2.5.1.2 and 4.2.5.1.3 deck cargo should

be included if such a practice is anticipated; .5 water ballast should normally only be included if carried in tanks

which are specially provided for this purpose. 4.2.6 Recommendation for an interim simplified stability criterion for decked fishing vessels under 24 m in length 4.2.6.1 For decked vessels with a length less than 30 m, the following approximate formula for the minimum metacentric height GMmin (in metres) for all operating conditions should be used as the criterion: GMmin = 0.53 + 2B [0.075-0.37(f)+0.82(f)2-0.014(B)-0.032(ls)] B B D L where: L is the length of the vessel on the waterline in maximum load

condition (in metres) ls is the actual length of enclosed superstructure extending from

side to side of the vessel (in metres) B is the extreme breadth of the vessel on the waterline in maximum load

condition (in metres) D is the depth of the vessel measured vertically amidships from the

base line to the top of the upper deck at side (in metres) f is the smallest freeboard measured vertically from the top of the

upper deck at side to the actual waterline (in metres)

The formula is applicable for vessels having: .1 f/B between 0.02 and 0.20; .2 ls/L smaller than 0.60; .3 B/D between 1.75 and 2.15; .4 sheer fore and aft at least equal to or exceeding the standard sheer prescribed in regulation 38(8) of the

International Convention on Load Lines, 1966; .5 height of superstructure included in the calculation not less than 1.8 m. For ships with parameters outside of the above limits the formula should be applied with special care. 4.2.6.2 The above formula is not intended as a replacement for the basic criteria given in 4.2.3 and 4.2.4 but is to be used

only if circumstances are such that cross curves of stability, KM curve and subsequent GZ curves are not and cannot be made

available for judging a particular vessel's stability. 4.2.6.3 The calculated value of GMmin should be compared with actual GM values of the vessel in all loading conditions. If a rolling test (see section 7.6), an inclining experiment based on estimated displacement or another approximate method of

determining the actual GM is used, a safety margin should be added to the calculated GMmin. 4.3 Special purpose ships 4.3.1 Application The provisions given hereunder apply to special purpose ships, as defined in 1.3.5, of not less than 500 tons gross

tonnage. The Administration may also apply these provisions as far as reasonable and practicable to special purpose ships of

less than 500 tons gross tonnage. 4.3.2 Stability criteria The intact stability of special purpose ships should comply with the provisions given in 3.1.2 except that the

alternative criteria given in 4.5.6.2 which apply to offshore supply vessels may be used for special purpose ships of less

than 100 m in length of similar design and characteristics. 4.4* Cargo ships carrying grain in bulk The intact stability of ships engaged in the carriage of grain should comply with the requirements of the

International Code for the Safe Carriage of Grain in Bulk adopted by resolution MSC.23(59).* * Refer to chapter VI of the 1974 SOLAS Convention and to part C of chapter VI of the 1974 SOLAS Convention as amended by

resolution MSC.22(59).

4.5 Offshore supply vessels 4.5.1 Application .1 The provisions given hereunder apply to offshore supply vessels,

as defined in 1.3.6, of 24 m in length and over. The alternative stability criteria contained in 4.5.6 apply to vessels of not more than 100 m in length.

.2 For a vessel engaged in near-coastal voyages, as defined in 4.5.2,

the principles given in 4.5.3 should guide the Administration in the development of its national standards. Relaxations from the requirements of the Code may be permitted by an Administration for vessels engaged in near-coastal voyages off its own coasts provided the operating conditions are, in the opinion of that Administration, such as to render compliance with the provisions of the Code unreasonable or unnecessary.

.3 Where a ship other than an offshore supply vessel, as defined in

1.3.6, is employed on a similar service, the Administration should determine the extent to which compliance with the provisions of the Code is required.

4.5.2 Definitions Near-coastal voyage means a voyage in the vicinity of the coast of a State as defined by the Administration of that State. 4.5.3 Principles governing near-coastal voyages .1 The Administration defining near-coastal voyages for the purpose

of the present Code should not impose design and construction for a vessel entitled to fly the flag of another State and engaged in such voyages in a manner resulting in a more stringent standard for such a vessel than for a vessel entitled to fly its own flag. In no case should the Administration impose, in respect of a vessel entitled to fly the flag of another State, standards in excess of the Code for a vessel not engaged in near-coastal voyages.

.2 With respect to a vessel regularly engaged in near-coastal voyages

off the coast of another State the Administration should prescribe design and construction standards for such a vessel at least equal to those prescribed by the Government of the State off whose coast the vessel is engaged, provided such standards do not exceed the Code in respect of a vessel not engaged in near-coastal voyages.

.3 A vessel which extends its voyages beyond a near-coastal voyage

should comply with the present Code. 4.5.4 Constructional precautions against capsizing .1 Access to the machinery space should, if possible, be arranged

within the forecastle. Any access to the machinery space from the exposed cargo deck should be provided with two weathertight closures. Access to spaces below the exposed cargo deck should preferably be from a position within or above the superstructure deck.

.2 The area of freeing ports in the side bulwarks of the cargo deck should at least meet the requirements of regulation 27 of the International Convention on Load Lines, 1966. The disposition of the freeing ports should be carefully considered to ensure the most effective drainage of water trapped in pipe deck cargoes or in recesses at the after end of the forecastle. In vessels operating in areas where icing is likely to occur, no shutters should be fitted in the freeing ports.

.3 The Administration should give special attention to adequate drainage

of pipe stowage positions having regard to the individual characteristics of the vessel. However, the area provided for drainage of the pipe stowage positions should be in excess of the required freeing port area in the cargo deck bulwarks and should not be fitted with shutters.

.4 A vessel engaged in towing operations should be provided with means

for quick release of the towing hawser. 4.5.5 Operational procedures against capsizing .1 The arrangement of cargo stowed on deck should be such as to avoid

any obstruction of the freeing ports or of the areas necessary for the drainage of pipe stowage positions to the freeing ports.

.2 A minimum freeboard at the stern of at least 0.005 L should be

maintained in all operating conditions. 4.5.6 Stability criteria .1 The stability criteria given in 3.1.2 should apply to all offshore

supply vessels except those having characteristics which render compliance with 3.1.2 impracticable.

.2 The following equivalent criteria are recommended where a vessel's

characteristics render compliance with 3.1.2 impracticable: .2.1 The area under the curve of righting levers (GZ curve) should

not be less than 0.070 metre-radians up to an angle of 15 when the maximum righting lever (GZ) occurs at 15 and 0.055 metre-radians up to an angle of 30 when the maximum righting lever (GZ) occurs at 30 or above. Where the maximum righting lever (GZ) occurs at angles of between 15 and 30, the corresponding area under the righting lever curve should be:

0.055 + 0.001 (30 - ?max) metre-radians* .2.2 The area under the righting lever curve (GZ curve) between the

angles of heel of 30 and 40, or between 30 and 0f if this angle is less than 40, should be not less than 0.03 metre-radians.

.2.3 The righting lever (GZ) should be at least 0.20 m at an angle of

heel equal to or greater than 30. * ?max is the angle of heel in degrees at which the righting lever curve

reaches its maximum.

.2.4 The maximum righting lever (GZ) should occur at an angle of heel not less than 15.

.2.5 The initial transverse metacentric height (GMo) should not be

less than 0.l5 m. .3 Reference is made also to recommendations contained in section 2.3

and paragraphs 3.1.2.7 to 3.1.2.9. 4.5.7 Loading conditions The standard loading conditions should be as follows: .1 Vessel in fully loaded departure condition with cargo distributed

below deck and with cargo specified by position and weight on deck, with full stores and fuel, corresponding to the worst service condition in which all the relevant stability criteria are met.

.2 Vessel in fully loaded arrival condition with cargo as specified

in .1, but with 10% stores and fuel. .3 Vessel in ballast departure condition, without cargo but with full

stores and fuel. .4 Vessel in ballast arrival condition, without cargo and with 10%

stores and fuel remaining. .5 Vessel in the worst anticipated operating condition. 4.5.8 Assumptions for calculating loading conditions The assumptions for calculating loading conditions should be as follows: .1 If a vessel is fitted with cargo tanks, the fully loaded conditions

of 4.5.7.1 and 4.5.7.2 should be modified, assuming first the cargo tanks full and then the cargo tanks empty.

.2 If in any loading condition water ballast is necessary, additional

diagrams should be calculated, taking into account the water ballast, the quantity and disposition of which should be stated in the stability information.

.3 In all cases when deck cargo is carried a realistic stowage weight

should be assumed and stated in the stability information, including the height of the cargo and its centre of gravity.

.4 Where pipes are carried on deck, a quantity of trapped water equal

to a certain percentage of the net volume of the pipe deck cargo should be assumed in and around the pipes. The net volume should be taken as the internal volume of the pipes, plus the volume between the pipes. This percentage should be 30 if the freeboard amidships is equal to or less than 0.015 L and 10 if the freeboard amidships is equal to or greater than 0.03 L. For intermediate values of the freeboard amidships the percentage may be obtained by linear interpolation. In assessing the quantity of trapped water, the Administration may take into account positive or negative sheer aft, actual trim and area of operation.

.5 If a vessel operates in zones where ice accretion is likely to occur, allowance for icing should be made in accordance with the provisions of chapter 5.

4.6 Mobile offshore drilling units (MODUs) 4.6.1 Application .1 The provisions given hereunder apply to mobile offshore drilling

units as defined in 1.3.7, the keels of which are laid or which are at a similar stage of construction on or after 1 May 1991. For MODUs constructed before that date, the corresponding provisions of chapter 3 of resolution A.414(XI) should apply.

.2 The coastal State may permit any unit designed to a lesser

standard than that of this chapter to engage in operations having taken account of the local environmental conditions. Any such unit should, however, comply with safety requirements which in the opinion of the coastal State are adequate for the intended operation and ensure the overall safety of the unit and the personnel on board.

4.6.2 Definitions For the purposes of this section, the terms used herein have the meanings defined in the following paragraphs: .1 coastal State means the Government of the State exercising

administrative control over the drilling operations of the unit; .2 mode of operation means a condition or manner in which a unit may

operate or function while on location or in transit. The modes of operation of a unit include the following:

.2.1 operating conditions - conditions wherein a unit is on location

for the purpose of conducting drilling operations, and combined environmental and operational loadings are within the appropriatedesign limits established for such operations. The unit may be either afloat or supported on the seabed, as applicable;

.2.2 severe storm conditions - conditions wherein a unit may be

subjected to the most severe environmental loadings for which the unit is designed. Drilling operations are assumed to have been discontinued due to the severity of the environmental loadings, the unit may be either afloat or supported on the seabed, as applicable;

.2.3 transit conditions - conditions wherein a unit is moving from

one geographical location to another. 4.6.3 Righting moment and heeling moment curves 4.6.3.1 Curves of righting moments and of wind heeling moments similar to figure 4.6-1 with supporting calculations should be prepared covering the full range of operating draughts including those in transit conditions, taking into account the maximum deck cargo and equipment in the most unfavourable position applicable. The righting moment curves and wind heeling moment curves should be related to the most critical axes. Account should be taken of the free surface of liquids in tanks.

Figure 4.6-1 - Righting moment and wind heeling moment curves 4.6.3.2 Where equipment is of such a nature that it can be lowered and stowed, additional wind heeling moment curves may be required and such data should clearly indicate the position of such equipment. 4.6.3.3 The curves of wind heeling moment should be drawn for wind forces calculated by the following formula: F = 0.5CsCH ? V2A (Newtons) where: F is the wind force (Newtons) Cs is the shape coefficient depending on the shape of the structural member exposed to the wind (see table 4.6-1) CH is the height coefficient depending on the height above sea level of the structural member exposed to wind (see table 4.6-2) ? is the air mass density (1.222 kilogrammes per cubic metre) V is the wind velocity (metres per second) A is the projected area of all exposed surfaces in either the upright or the heeled condition (square metres)

Table 4.6-1 Values of the coefficient Cs

Shape Cs

Spherical Cylindrical Large flat surface (hull, deckhouse, smooth under-deck areas) Drilling derrick Wires Exposed beams and girders under deck Small parts Isolated shapes (crane, beam, etc.) Clustered deckhouses or similar structures

0.4 0.5 1.0 1.25 1.2 1.3 1.4 1.5 1.1

Table 4.6-2 Values of the coefficient CH

Height above sea level (metres) CH

0 - 15.3 15.3- 30.5 30.5- 46.0 46.0- 61.0 61.0- 76.0 76.0- 91.5 91.5-106.5 106.5-122.0 122.0-137.0 137.0-152.5 152.5-167.5 167.5-183.0 183.0-198.0 198.0-213.5 213.5-228.5 228.5-244.0 244.0-256.0 above 256

1.00 1.10 1.20 1.30 1.37 1.43 1.48 1.52 1.56 1.60 1.63 1.67 1.70 1.72 1.75 1.77 1.79 1.80

4.6.3.4 Wind forces should be considered from any direction relative to the unit and the value of the wind velocity should be as follows: .1 In general a minimum wind velocity of 36 m/s (70 knots) for offshore

service should be used for normal operating conditions and a minimum wind velocity of 51.5 m/s (100 knots) should be used for the severe storm conditions.

.2 Where a unit is to be limited in operation to sheltered locations

(protected inland waters such as lakes, bays, swamps, rivers, etc.) consideration should be given to a reduced wind velocity of not less than 25.8 m/s (50 knots) for normal operating conditions.

4.6.3.5 In calculating the projected areas to the vertical plane, the area of surfaces exposed to wind due to heel or trim, such as under decks, etc., should be included using the appropriate shape factor. Open truss work may be approximated by taking 30% of the projected block area of both the front and back section, i.e. 60% of the projected area of one side. 4.6.3.6 In calculating the wind heeling moments, the lever of the wind overturning force should be taken vertically from the centre of pressure of all surfaces exposed to the wind to the centre of lateral resistance of the underwater body of the unit. The unit is to be assumed floating free of mooring restraint. 4.6.3.7 The wind heeling moment curve should be calculated for a sufficient number of heel angles to define the curve. For ship-shaped hulls the curve may be assumed to vary as the cosine function of ship heel. 4.6.3.8 Wind heeling moments derived from wind tunnel tests on a representative model of the unit may be considered as alternatives to the method given in 4.6.3.3 to 4.6.3.7. Such heeling moment determination should include lift and drag effects at various applicable heel angles.

4.6.4 Intact stability criteria 4.6.4.1 The stability of a unit in each mode of operation should meet the following criteria (see also figure 4.6-2): .1 For surface and self-elevating units the area under the righting

moment curve to the second intercept or downflooding angle, whichever is less, should be not less than 40% in excess of the area under the wind heeling moment curve to the same limiting angle.

.2 For column-stabilized units the area under the righting moment curve

to the angle of downflooding should be not less than 30% in excess of the area under the wind heeling moment curve to the same limiting angle.

.3 The righting moment curve should be positive over the entire range of

angles from upright to the second intercept. 4.6.4.2 Each unit should be capable of attaining a severe storm condition in a period of time consistent with the meteorological conditions. The procedures recommended and the approximate length of time required, considering both operating conditions and transit conditions, should be contained in the operating manual, as referred to in 2.1.2. It should be possible to achieve the severe storm condition without the removal or relocation of solid consumables or other variable load. However, the Administration may permit loading a unit past the point at which solid consumables would have to be removed or relocated to go to severe storm condition under the following conditions, provided the allowable KG requirement is not exceeded: .1 in a geographic location where weather conditions annually or

seasonally do not become sufficiently severe to require a unit to go to severe storm condition; or

.2 where a unit is required to support extra deckload for a short

period of time that is well within the bounds of a favourable weather forecast.

The geographic locations and weather conditions and loading conditions when this is permitted should be identified in the operating manual. 4.6.4.3 Alternative stability criteria may be considered by the Administration provided an equivalent level of safety is maintained and if they are demonstrated to afford adequate positive initial stability. In determining the acceptability of such criteria, the Administration should consider at least the following and take into account as appropriate: .1 environmental conditions representing realistic winds (including

gusts) and waves appropriate for world-wide service in various modes of operation;

.2 dynamic response of a unit. Analysis should include the results of

wind tunnel tests, wave tank model tests, and non-linear simulation, where appropriate. Any wind and wave spectra used should cover sufficient frequency ranges to ensure that critical motion responses are obtained;

.3 potential for flooding taking into account dynamic responses in a seaway;

.4 susceptibility to capsizing considering the unit's restoration energy

and the static inclination due to the mean wind speed and the maximum dynamic response;

.5 an adequate safety margin to account for uncertainties. An example of alternative criteria for twin-pontoon column-stabilized semi-submersible units is given in section 4.6.5. 4.6.5 An example of alternative intact stability criteria for twin-pontoon column-stabilized semi-submersible units 4.6.5.1 The criteria given below apply only to twin-pontoon column-stabilized semi-submersible units in severe storm conditions which fall within the following range of parameters: Vp/Vt is between 0.48 and 0.58 Awp/(Vc)2/3 is between 0.72 and 1.00 Iwp/[Vc x (Lptn/2)] is between 0.40 and 0.70 The parameters used in the above equations are defined in paragraph 4.6.5.3. 4.6.5.2 Intact stability criteria The stability of a unit in the survival mode of operation should meet the following criteria: .1 Capsize criteria These criteria are based on the wind heeling moment and

righting moment curves calculated as shown in section 4.6.3 of the Code at the survival draught. The reserve energy area 'B' must be greater than 10% of the dynamic response area 'A' as shown in figure 4.6-3.

Area 'B'/Area 'A' 0.10 Where: Area 'A' is the area under the righting arm curve measured from ?1 to (?1 + 1.15 ?dyn) Area 'B' is the area under the righting arm curve measured from (?1 + 1.15 ?dyn) to ?2 ?1 is the first intercept with the 100 knot wind moment curve ?2 is the second intercept with the 100 knot wind moment curve ?dyn is the dynamic response angle due to waves and fluctuating wind ?dyn= (10.3 + 17.8C)/(1 + GM/(1.46 + 0.28BM)) C = (Lptn 5/3 * VCPw1 * Aw * Vp * Vc 1/3)/(Iwp 5/3 * Vt)

Parameters used in the above equations are defined in paragraph 4.6.5.3. .2 Downflooding criteria These criteria are based on the physical dimensions of the unit

and the relative motion of the unit about a static inclination due to a 75 knot wind measured at the survival draught. The initial downflooding distance (DFDo) should be greater than the reduction in downflooding distance at the survival draught as shown in figure 4.6-4.

DFDo - RDFD 0.0 Where: DFDo is the initial downflooding distance to Dm in metres RDFD is the reduction in downflooding distance in metres equal to SF (k * QSD1 + RMW) SF is equal to 1.10, which is a safety factor to account for uncertainties in the analysis, such as non-linear effects. k (correlation factor) is equal to 0.55 + 0.08 (a - 4.0) + 0.056 (1.52 - GM) a is equal to (FBDo/Dm)(Sptn * Lccc)/Awp (a cannot be taken to be less than 4.0) (GM cannot be taken to be greater than 2.44 m) QSD1 is equal to DFDo - quasi-static downflooding distance at ?1, in metres, but not to be taken less than 3.0 m. RMW is the relative motion due to waves about ?1 in metres, equal to 9.3 + 0.11(X-12.19) X is equal to Dm(Vt/Vp)(Awp 2/Iwp)(Lccc/Lptn) (X cannot be taken to be less than 12.19 m) The parameters used in the above equations are defined in paragraph 4.6.5.3. 4.6.5.3 Geometric parameters Awp is the waterplane area at the survival draught including the effects of

bracing members as applicable (in square metres). Aw is the effective wind area with the unit in the upright position

(i.e. the product of projected area, shape coefficient and height coefficient) (in square metres).

BM is the vertical distance from the metacentre to the centre of

buoyancy with the unit in the upright position (in metres). Dm is the initial survival draught (in metres). FBDo is the vertical distance from Dm to the top of the upper exposed

weathertight deck at the side (in metres). GM for paragraph 4.6.5.2.1, GM is the metacentric height measured about

the roll or diagonal axis, whichever gives the minimum restoring energy ratio, 'B'/'A'. This axis is usually the diagonal axis as it possesses a characteristically larger projected wind area which influences the three characteristic angles mentioned above.

GM for paragraph 4.6.5.2.2, GM is the metacentric height measured about the axis which gives the minimum downflooding distance margin (i.e. generally the direction that gives the largest QSD1) (in metres).

Iwp is the waterplane second moment of inertia at the survival draught

including the effects of bracing members as applicable (in metres to the power of 4).

Lccc is the longitudinal distance between centres of the corner columns (in

metres). Lptn is the length of each pontoon (in metres). Sptn is the transverse distance between the centreline of the pontoons (in

metres). Vc is the total volume of all columns from the top of the pontoons to

the top of the column structure, except for any volume included in the upper deck (in cubic metres).

Vp is the total combined volume of both pontoons (in cubic metres). Vt is the total volume of the structures (pontoons, columns and

bracings) contributing to the buoyancy of the unit, from its baseline to the top of the column structure, except for any volume included in the upper deck (in cubic metres).

VCPw1 is the vertical centre of wind pressure above Dm (in metres).

Figure 4.6-4 - Definition of downflooding distance and relative motion

4.6.5.4 Capsize criteria assessment form Input data GM = m BM = m VCPwl = m Aw = m2 Vt = m3 Vc = m3 Vp = m3 Iwp = m4 Lptn = m Determine ?1 = deg ?2 = deg C = (Lptn 5/3 * VCPw1 * Aw * Vp * Vc 1/3)/(Iwp 5/3 * Vt) = m-1 ?dyn = (10.3 + 17.8C)/(1.0 + GM/(1.46 + 0.28BM)) = deg Area 'A' = m-deg Area 'B' = m-deg Results Reserve energy ratio: 'B'/'A' = (min = 0.10) GM = m (KG = m) Note: The minimum GM is that which produces a 'B'/'A' ratio = 0.10 4.6.5.5 Downflooding criteria assessment form Input data

DFDo = m

FBDo = m

GM = m

Dm = m

Vt = m3

Vp = m3

Awp = m2

Iwp = m4

Lccc = m

Lptn = m

Sptn = m

SF = = 1.10

Determine ?1 deg DFD1 m QSD1= DFDo - DFD1 m a = (FBDo/Dm)(Sptn * Lccc)/Awp = (AMIN = 4.0) k = 0.55 + 0.08(a-4.0) + 0.056(1.52-GM) = (GMMAX = 2.44 m) X = Dm(Vt/Vp)(Awp 2/Iwp)(Lccc/Lptn)= m = (XMIN=12.19 m) RMW = 9.3 + 0.11(X-12.19) = m RDFD = SF (k * QSD1 + RMW) = m Results Downflooding margin: DFDo - RDFD = (min = 0.0 m) GM = m (KG = m) Note: The minimum GM is that which produces a downflooding margin = 0.0 m. 4.7 Pontoons 4.7.1 Application The provisions given hereunder apply to seagoing pontoons. A pontoon is considered to be normally: .1 non self-propelled; .2 unmanned; .3 carrying only deck cargo; .4 having a block coefficient of 0.9 or greater; .5 having a breadth/depth ratio of greater than 3.0; and .6 having no hatchways in the deck except small manholes closed

with gasketed covers. 4.7.2 Stability drawings and calculations 4.7.2.1 The following information is typical of that required to be submitted to the Administration for approval: .1 lines drawing; .2 hydrostatic curves; .3 cross curves; .4 report of draught and density readings and calculation of

lightship displacement and longitudinal centre of gravity; .5 statement of justification of assumed vertical centre of

gravity; .6 simplified stability guidance such as a loading diagram, so

that the pontoon may be loaded in compliance with the stability criteria.

4.7.2.2 Concerning the performance of calculations, the following is suggested: .1 no account should be taken of the buoyancy of deck cargo (unless

buoyancy credit for adequately secured timber); .2 consideration should be given to such factors as water absorption

(e.g. timber), trapped water in cargo (e.g. pipes) and ice accretion; .3 in performing wind heel calculations: .3.1 the wind pressure should be constant and for general operations

be considered to act on a solid mass extending over the length of the cargo deck and to an assumed height above the deck,

.3.2 the centre of gravity of the cargo should be assumed at a point

mid-height of the cargo, and .3.3 the wind lever arm should be taken from the centre of the

deck cargo to a point at one half the draught; .4 calculations should be performed covering the full range of

operating draughts; .5 the downflooding angle should be taken as the angle at which an

opening through which progressive flooding may take place is immersed. This would not be an opening closed by a watertight manhole cover or a vent fitted with an automatic closure.

4.7.3 Intact stability criteria 4.7.3.1 The area under righting lever curve up to the angle of maximum righting lever should not be less than 0.08 metre-radians. 4.7.3.2 The static angle of heel due to a uniformly distributed wind load of 0.54 kPa (wind speed 30 m/s) should not exceed an angle corresponding to half the freeboard for the relevant loading condition, where the lever of wind heeling moment is measured from the centroid of the windage area to half the draught. 4.7.3.3 The minimum range of stability should be: For L 100 m 20 For L 150 m 15 For intermediate length by interpolation. Note: As the Code of Safety for Dynamically Supported Craft

(resolution A.373(X)) is under current revision, the provisions given below are of an interim nature. In particular, such factors as the increase in the number of passengers carried on board and new types of DSC are expected to be among major changes to be introduced into a new code. When the revision of the Intact Stability Code is undertaken, the standards for such craft will be replaced by the provisions of the High Speed Craft (HSC) Code currently under development.

4.8 Dynamically supported craft (DSC) 4.8.1 Application 4.8.1.1 The provisions given hereunder apply to dynamically supported craft as defined in 1.3.8 which are engaged on voyages between a terminal in one country and a terminal in another country, part or all of which voyages are across areas of water (but not necessarily on routes navigable to ships) through which a ship operating on an international voyage, as defined in regulation I/2(d) of the 1974 SOLAS Convention, as amended, would proceed. In applying the provisions of this chapter, the Administration should determine whether a craft is a dynamically supported craft as defined in 1.3.8, or whether its characteristics are such that the SOLAS and Load Line Conventions can be applied. For novel types of DSC other than defined in 1.3.9 and 1.3.10, the Administration should determine the extent to which the provisions of this chapter are applicable to those novel types. The contents of this chapter should be applied by Administrations through more detailed national regulations based on a comprehensive coverage of the provisions contained therein. 4.8.1.2 The provisions in this chapter apply to DSC which: .1 carry more than 12 passengers but not more than 450 passengers

with all passengers seated; .2 do not proceed in the course of their voyage more than

100 nautical miles from the place of refuge; and .3 may be provided within the limits of subparagraphs .1 and .2

with special category spaces intended to carry motor vehicles with fuel in their tanks.

The provisions given below may be extended to a DSC which is intended to carry passengers and cargo or solely cargo or to a craft which exceeds the limits specified in .1 to .3. In such cases, the Administration should determine the extent to which the provisions of the Code are applicable to these craft and, if necessary, develop additional requirements providing the appropriate safety level for such craft. 4.8.2 General provisions 4.8.2.1 A craft should be provided with: .1 stability characteristics and stabilization systems adequate

for safety when the craft is operated in the non-displacement mode and during the transient mode; and

.2 buoyancy and stability characteristics adequate for safety where

the craft is operated in the displaced mode both in the intact condition and the damage condition.

4.8.2.2 If a craft operates in zones where ice accretion is likely to occur, the effect of icing should be taken into account in the stability calculations in accordance with section 5.5.

4.8.3 Definitions For the purpose of this chapter, unless expressly defined otherwise, the following definitions apply: .1 length (L) means length of the rigid hull measured on the design

waterline in the displacement mode; .2 breadth (B) means breadth of the broadest part of the rigid hull

measured on the design waterline in the displacement mode; .3 design waterline means the waterline corresponding to the loaded

displacement of the craft when stationary; .4 weathertight means that water will not penetrate into the craft

in any wind and wave conditions up to those specified as critical design conditions;

.5 skirt means a downwardly-extending, flexible structure used to

contain or divide an air cushion; .6 fully submerged foil means a foil having no lift components

piercing the surface of the water in the foil-borne mode. 4.8.4 Intact buoyancy 4.8.4.1 The craft should have a designed reserve of buoyancy when floating in seawater of not less than 100% at the maximum operational weight. The Administration may require a larger reserve of buoyancy to permit the craft to operate in any of its intended modes. The reserve of buoyancy should be calculated by including only those compartments which are: .1 watertight; .2 considered by the Administration to have scantlings and

arrangements adequate to maintain their watertight integrity; and .3 situated below a datum, which may be a watertight deck or

equivalent structure watertight longitudinally and transversely and from at least part of which the passengers would be disembarked in an emergency.

4.8.4.2 Means should be provided for checking the waterti